Even if i could agree with previous answer, i have to notice something :
Statistics !
Even if it is Full random like a dice : it is POSSIBLE to get fifty 1 on a dice an no 6 .
So 10 hours isnt enough, farm something like 1000h, then compil your statistic, and calculate your Gauss proability to be or not to be random.
I am positive that there is some code or player-based randomization within the drops for mutated animals. I go can out with shotguns in factory rad. town for literally 10+ hours, and will never see anything but the same drops. Like, I never see leather or radiation bodies/helmets, but will find a million boots and legs. Also, I have got 11 kevlar boots, 3 kevlar pants, but nothing else so far (not even a single metal structure drop or other piece of kevlar).
I can't tell if certain zones drop certain items, or there is something to cause/encourage players to interact with each other by having different drop rates for each player. Has anybody else experienced this?